Why does Pesach begin on the 15th of Nisan when Numbers 28:16 says “And in the first month, on the fourteenth day of the month, is the LORD’S passover”?

Special thanks to Rabbi George Schlesinger for this guest post.

First of all, it’s helpful to know and understand the Hebrew and to know that in ancient days there were two sacrifices i.e. two holidays that were conjoined into one in later days. There was the Pascal sacrifice/Pascal holiday which was known as the “Pesach” or “passover.” This was an agricultural holiday celebrating springtime and the new lambs of the flock and it apparently preceded the Exodus from Egypt by many, many years. That sacrifice/holiday was on the 14th of Nisan. And it’s the term that in later days came to be used in Judaism for what was in ancient times a separate sacrifice/holiday celebrated a day later…the 15th of Nisan and the start of a 7 day festival during which matza was eaten. The holiday celebrating the Exodus is (in the Bible) usually called Chag HaMatzot or Festival of Matzah. So a more precise translation of verses 16 and 17 would read:

“The day of the paschal offering and the seven-day Festival of Unleavened Bread are discrete holidays. Yet the fact that the paschal offering is mentioned even though it is a private sacrifice (see Exodus 12:1-11) –– and hence no description is given –– indicates that the two festivals are already fused.”

In later centuries, the two sacrifices were both made on the 14th of Nisan. The “pesach”/paschal offering earlier in the day than the offering for the Chag HaMatzot since that was the lamb that was to be eaten at the Seder commemorating the Exodus and it had to be slaughtered and roasted prior to sundown of the 15th so that it could be consumed during the Seder.

In general, Jewish Holidays begin the evening before the date specified. This is because the Jewish day actually begins at sundown on the previous night. Sometimes, for clarity, the Erev holiday is also included to indicate that the holiday begins the evening before.

For example, in the April 2015 calendar below, Erev Pesach is listed as April 3rd and the first day of Pesach is listed as April 4th. This means that the holiday of Pesach begins on the evening on April 3rd.

And, Rosh Chodesh Iyyar is listed on April 19. This means that Rosh Chodesh begins on the evening of April 18, even though the Erev is not explicitly mentioned on the calendar.

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Note the latitude/longitude represented in “degrees minutes direction” (in the example of Ixiamas, La Paz, Bolivia it is Lat: 13 45 S and Long: 068 10 W) and write this information down on a sheet of paper